While this is track and vehicle dependent a user can expect something close to these approximations on RAM use:
Approximately 200 MB per server instance for server populations less than 10
Approximately 300 MB per server instance for server populations between 10 and 20
Approximately 400 MB per server instance for server populations between 20 and 30

CPU Usage:
This is also dependent on the server population and number of AI drivers but we would account for at least 250 MHz per server instance and on modern CPU, for example if you have a 2.5 GHz dual core you can run 20 servers (10 per core, 10 * 250 Mhz = 2.5 GHz) on that CPU if you have other requirements mentioned above meet. Floating point unit required.

These are just guide lines, there are many things that can effect performance of the server.

I don't see a problem with such traffic. We want quality, we must pay for that some price.
Maybe in future it will be optimized a bit. But if you take into account sending data about RealTrack and weather (in both cases for each point of track separately) and more info about telemetry (e.g. better suspension work) there is no way to avoid it.
I also suspect those are aproximated maximal requirements. Maybe there will be possibility to set some kind of throttling or limit precision of sent data.